Roller driven devices are known, each of them comprising a tubular cylindrical roller supported, through bearing, by an axis or by another kind of support. Each end of the roller is provided with a respective wheel or bushing (in the following the latter element will be named “wheel”). The known devices further comprise a single or double pulley fixed to the external surface of the cylindrical roller adjacent to one of the side wheels. The pulley usually is a timing pulley for timing belts, and it transmits to the device the motion for the rotation of the device around the axis of the roller provided by the belt engaged to the drive pulley of an engine.
In some of the roller devices the pulley is fixed closer to the respective wheel, and it is fixed to the roller by means of an annular welding made at the external end, in other words, at the end close to the wheel, of the pulley whose opposite end is not welded to preserve the roller strength in its area more affected by flexion and stresses. This avoids weakening of the roller but because of the close distance between the pulley and the adjacent inner flange of the wheel, does not allow to weld the inner flange to the roller on the contrary to the inner flange of the opposite wheel of the device.
A drawback of the known solution consists in that, in the event of abnormal and/or very high and/or axial components stresses, acting on the wheel adjacent to the pulley, the connection between the wheel and the roller could be damaged.
U.S. Appl. Publ. No. 2008/0010831 discloses a process for making a roller for conveying products along a predetermined path in an industrial installation, where a portion for rotationally driving the roller includes a tubular element and is associated with a rotatable roller support of the same roller in the form of a long tubular body.
U.S. Appl. Publ. No. 2006/0102451 discloses roller driven device for roller conveyors comprising a tubular roller, freely rotating around its geometric axis and having at each end a respective lateral wheel each comprising a tubular cylindrical element having an external protruding flange and an internal flange where the tubular cylindrical element and the two flanges are integral. The roller driven device comprises a timing pulley adjacent to a first lateral wheel and a sleeve inside the timing pulley and to the first lateral wheel and containing a respective end of the tubular roller. The end of the tubular roller is welded to the inner surface of the sleeve. The end of the sleeve can be welded inside the inner cavity of the first wheel (as shown in FIGS. 1A and 1B of document U.S. Appl. Publ. No. 2006/0102451) or to the side external surface of the external protruding flange of the first wheel (as shown in FIGS. 2A and 2B of document U.S. Appl. Publ. No. 2006/102451). In this latter case, the end of the roller and the respective welding to the inner surface of the sleeve is quite deep inside the sleeve, at least to leave space for the bearings.
Both solutions are affected by the difficulty of carrying out inner weldings.
A further drawback of both solutions consists in that no direct welding or direct fixing are carried out between the roller and the first wheel.
Another drawback of both solutions consists in that provide only one (indirect) connection between the roller and the first wheel.
A further drawback of both solutions consists in that the end of the sleeve opposed to the first wheel must be welded to the roller close to the median portion thereof, increasing the risks to weaken the roller in the critical position.
A drawback of the first known solution consists in that the first wheel must be solid to provide the welding surface, and must be complex and expensive because of the bearing housing carried out in the body of the first wheel.
A drawback of the second known solution consists in that the fixing of the first wheel to the roller is made by two sequential and spaced welding increasing the risk of mispositioning and/or misalignment.